fix(core): a resumed session's /context prices the memory index it carries

[Max17190]

Why

Round-5 ticket T4 (.scratch/selfext-round5/findings.md). PromptBreakdown::from_persisted fills tools and skills from the frozen registry but left memory empty, while the persisted prompt it prices carries the memory section. After a resume that does not refreeze, /context showed zero memory rows for bytes paid on every request.

Summary

• from_persisted takes the persisted prompt text (it previously took only its length) and parses the memory rows from the prompt's own bytes: the section header (now a shared const, so assembly and parser cannot drift) followed by consecutive - name: description — path lines. Each row is priced as the line length including its newline, the exact accounting the live scan records.
• Parsing the prompt rather than re-scanning disk is deliberate: a manifest-restored registry holds no memory section, and a fresh scan would price today's selection instead of the lines the prefix actually pays for.

Test Plan

• a_persisted_breakdown_prices_the_memory_index_it_carries: two memories; the resumed breakdown's rows must equal the live scan's rows exactly (names and byte costs), and a prompt with no section prices none. Red against the previous no-fill behavior (verified).
• Existing skills half of the accounting test updated to the new signature and still asserts resumed == fresh.
• Full workspace green (exit 0), clippy zero warnings.

Greptile Summary

Resumed /context accounting now uses the memory-index rows captured when the session prompt was frozen. The manifest preserves those rows across restoration, preventing prompt content from changing the displayed memory costs.

Confidence Score: 5/5

No blocking failure remains.

Focused manifest round-trip and forged-prompt tests passed, confirming that restored accounting retains freeze-time rows and does not interpret prompt bytes.

T-Rex Logs

What T-Rex did

• Validated that the restored-accounting path reads rows from Registry::frozen_memory_rows and that these rows are serialized as RegistryManifest::memory_rows and restored without parsing prompt text.
• Validated that breakdown.memory is assigned directly from registry.frozen_memory_rows and serialized/restored through RegistryManifest::memory_rows.
• Observed that both captured commands exited with code 0 and each had one targeted test passing.
• Noted that the persisted evidence files were saved and checksum-matched their original captured logs.

_{Ran code and verified through T-Rex}

_{Reviews (6): Last reviewed commit: "Merge remote-tracking branch 'origin/mai..." | Re-trigger Greptile}